Need IP's and connectivity

Some assistance Please
My setup consists of about 50 workstations, all running 98.
(IBM's/P2's) All are configured on the same subnet, -> ex.
(10.18.x.y ; 10.18.x.z etc. Subnet-> 255.255.240.0) and
are setup in about six workgroups. They belong to a
wireless LAN using Cisco 350 series LAN Adapters, and they
have connectivity to the internet thru these cards also.
There is an NT 4.0 Server (that is their default gateway
(10.18.96.1) that I have access to. Their DNS and DHCP
Servers' IP addresses read (10.128.5.30 and 10.128.5.28)
These, I do not have access to, due to the fact that I
don't know where they are.
Some machines point to only one IP address for
both duties, some of the machines point to one IP for DNS
and the other IP for DHCP.

There are two IBM's that have lost their way. They both
have lost connectivity to their respective workgroup and
internet. I have found out that ONE of them was sharing
the same IP as one of the others. (I don't know how) I ran
winipcfg and found that it's pointing to the same DCHP and
DNS servers as the others that are on the network, but it
doesnt have connectivity with them. THEN I learned that
NONE of the machines can ping the DNS or the DHCP.
There's 0% connectivity to these IPs. Now from what I have
learned thus far, my understanding is that there should be
connection at all times. How else would a machine get an
IP if needed?

Now I've found out that the 2nd machine that has
(lost it's way) was on a different subnet altogether.
(Once again, don't know how) BOTH machines were fine in
the beginning. I attempted to "release all" and "renew
all" both of them and >ofcourse< didn't get a useable IP
due to the non-connectivity. This is how I found out that
there was no connection to either server.

I am TOTALLY BEFUDDLED. Could someone put some (or a
bunch) of light on this situation for me please??? What
did I fall asleep on in class that I should have been
paying attention to AND how do I get these two machines
back online again with everybody else and the internet.

Hope I inputted enough information, I know I've left
something out.
THANX N ADVANCE The Rookie / Wayne B.